Enable CVO by default through webrtc pipeline.

All RTP packets from sender side will carry the rotation info. (will file a bug to track this) On the receiving side, only packets with marker bit set will be examined.

Tests completed:
1. android standalone to android standalone
2. android standalone to chrome (with and without this change)
3. android on chrome

BUG=4145
R=glaznev@webrtc.org, mflodman@webrtc.org, perkj@webrtc.org, pthatcher@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/47399004

Cr-Commit-Position: refs/heads/master@{#8905}

webrtc/modules/video_coding/main/source/packet.cc

@@ -99,6 +99,9 @@ void VCMPacket::Reset() {
 }
 
 void VCMPacket::CopyCodecSpecifics(const RTPVideoHeader& videoHeader) {
+  if (markerBit) {
+    codecSpecificHeader.rotation = videoHeader.rotation;
+  }
   switch (videoHeader.codec) {
     case kRtpVideoVp8:
       // Handle all packets within a frame as depending on the previous packet